<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<meta name="viewport" content="width=device-width, initial-scale=1">
		<title>My web site</title>
		<style type="text/css">
			.father{
				width: 500px;
				height: 300px;
				background: #ccc;
			}
			.son{
				padding: 10px 0;
				background: green;
			}
		</style>
	</head>
	<body>
		<div class="father">
			<div class="son"></div>
		</div>
	</body>
</html>